The protests have left five people dead and more than 200 wounded in street violence, although tensions had abated since several days of clashes between police and demonstrators in early December.

Yingluck has called a snap election for February 2 to try to ease tensions, but the main opposition Democrat Party — which has not won an elected majority in about two decades — has vowed to boycott the vote.

The latest confrontation came as representatives of about 30 political parties gathered inside a Bangkok stadium for a draw for the numbers to be used on the ballot sheets.

The demonstrators have vowed to keep up their campaign to disrupt the polls, with protest leader Suthep Thaugsuban threatening to “shut down the country” to prevent people voting.

Thailand has seen several bouts of political turmoil since Yingluck’s older brother Thaksin Shinawatra was ousted as premier in a military coup in 2006.

The political conflict broadly pits a Bangkok-based middle class and royalist elite, backed by the military, against rural and working-class voters loyal to Thaksin, who lives in self-exile.